adding colors to the text output during an etch run

this colorizes the following:

red:
  * test failures
  * post failures
  * all other raises and errors[1]

green:
  * setup commands (the actual command that will be run)
  * pre commands (the actual command that will be run)
  * test commands (the actual command that will be run)
  * post commands (the actual command that will be run)

yellow:
  * warnings

blue:
  * diff output

1 - I think I tracked them all down. there were a few that I was unsure of whether they could be colorized and I didn't really have a way to trigger them, so I played it safe and left them without color. I might need some help finding the things I missed that were not obvious.